This section provides background information related to the present disclosure which is not necessarily prior art.
In a long term evolution (LTE) time division duplex (TDD) system, a user equipment (UE, i.e., a user terminal device) may feed back acknowledgement (ACK)/negative acknowledgement (NACK) corresponding to multiple downlink subframes in an uplink subframe. After finishing the demodulation and decoding of the data in downlink subframes n-k, the UE feeds back signaling (i.e. ACK/NACK) in uplink subframe n to the base station in order to indicate whether data in the downlink subframe needs to be retransmitted, where kεK, and the value of the set K is related to the TDD uplink (UL)-downlink (DL) configuration adopted by the system and the subframe index, as shown in Table 1.
The “feedback window” refers to K downlink subframes corresponding to the same uplink subframe.
Table 1 Downlink association set index K: {k0, k1, . . . kM-1} for TDD
UL-DLSubframe nConfiguration01234567890——6—4——6—41——7, 64———7, 64—2——8, 7, 4, 6————8, 7, 4, 6——3——7, 6, 116, 55, 4—————4——12, 8, 7, 116, 5, 4, 7——————5——13, 12, 9, 8,———————7, 5, 4, 11, 66——775——77—
Two ACK/NACK feedback modes are supported by an LTE TDD system, i.e., ACK/NACK multiplexing and ACK/NACK bundling. For TDD UL-DL configuration 5, only ACK/NACK bundling is supported. The feedback mode adopted by a UE with ACK/NACK transmission is configured by higher layer signaling. When physical uplink control channel (PUCCH) format 1a/1b is used by a UE to feed back ACK/NACK, PUCCH format 1a/1b resource can be obtained through the following two manners according to the type of the data.
According to manner one, PUCCH resources corresponding to a semi-persistent scheduling (SPS) physical downlink shared channel (PDSCH) is configured semi-statically by higher layer.
According to manner two, PUCCH resources corresponding to a dynamically scheduled PDSCH or a physical downlink control channel (PDCCH) indicating SPS release is determined by the index of the first control channel element (CCE) occupied by the PDCCH.
When an LTE UE is configured with the ACK/NACK bundling with ACK/NACK transmission, the ACK/NACKs corresponding to codewords with the same index are bundled (i.e., logical AND) across the feedback window. FIG. 1 is a schematic diagram illustrating a conventional ACK/NACK bundling scheme.
For a single codeword transmission, 1-bit bundled ACK/NACK can be obtained and PUCCH format 1a is used for transmission. For multi-codeword (two codewords) transmissions, 2-bit bundled ACK/NACK can be obtained and PUCCH format 1b is used for transmission. The UE determines whether data is missed by the downlink assignment index (DAI) in a PDCCH. As shown in FIG. 1, the DAI value indicates the index of the dynamically scheduled downlink subframe in the current feedback window. The UE transmits bundled ACK/NACK using the uplink control channel resource corresponding to the PDCCH in which the DL DAI value is equal to 1.
When an LTE UE is configured with ACK/NACK multiplexing with ACK/NACK transmission, for the uplink subframe with M>1, where M is defined in Table 1, the ACK/NACKs corresponding to the multiple codewords in each DL subframe are bundled (i.e., spatial bundling), and NACK/discontinuous transmission (DTX) is generated as feedback information for the downlink subframe in which data is not received. FIG. 2 is a schematic diagram illustrating a conventional ACK/NACK multiplexing scheme. As such, M-bit ACK/NACK can be obtained and transmitted using PUCCH format 1b with channel selection according to the mapping relations as shown in Tables 2-4.
nPUCCH,x(1) represents PUCCH resources corresponding to HARQ-ACK(x), and DTX indicates the data packet is not received. 2-bit information b(0) and b(1) and PUCCH resource used for transmission are obtained by looking up the table based on the state composed by M feedback bits. When M=1, the UE directly transmits a 1-bit or 2-bit ACK/NACK using PUCCH format 1a/1b in the only one available channel.
TABLE 2LTE Rel-8/9 ACK/NACK mapping table, M = 2HARQ-ACK(0), HARQ-ACK(1)nPUCCH(1)b(0), b(1)ACK, ACKnPUCCH,1(1)1, 1ACK, NACK/DTXnPUCCH,0(1)0, 1NACK/DTX, ACKnPUCCH,1(1)0, 0NACK/DTX, NACKnPUCCH,1(1)1, 0NACK, DTXnPUCCH,0(1)1, 0DTX, DTXN/AN/A
TABLE 3LTE Rel-8/9 ACK/NACK mapping table, M = 3HARQ-ACK(0), HARQ-ACK(1),HARQ-ACK(2)nPUCCH(1)b(0), b(1)ACK, ACK, ACKnPUCCH,2(1)1, 1ACK, ACK, NACK/DTXnPUCCH,1(1)1, 1ACK, NACK/DTX, ACKnPUCCH,0(1)1, 1ACK, NACK/DTX, NACK/DTXnPUCCH,0(1)0, 1NACK/DTX, ACK, ACKnPUCCH,2(1)1, 0NACK/DTX, ACK, NACK/DTXnPUCCH,1(1)0, 0NACK/DTX, NACK/DTX, ACKnPUCCH,2(1)0, 0DTX, DTX, NACKnPUCCH,2(1)0, 1DTX, NACK, NACK/DTXnPUCCH,1(1)1, 0NACK, NACK/DTX, NACK/DTXnPUCCH,0(1)1, 0DTX, DTX, DTXN/AN/A
TABLE 4LTE Rel-8/9 ACK/NACK mapping table, M = 4HARQ-ACK(0), HARQ-ACK(1), HARQ-ACK(2),b(0),HARQ-ACK(3)nPUCCH(1)b(1)ACK, ACK, ACK, ACKnPUCCH,1(1)1, 1ACK, ACK, ACK, NACK/DTXnPUCCH,1(1)1, 0NACK/DTX, NACK/DTX, NACK, DTXnPUCCH,2(1)1, 1ACK, ACK, NACK/DTX, ACKnPUCCH,1(1)1, 0NACK, DTX, DTX, DTXnPUCCH,0(1)1, 0ACK, ACK, NACK/DTX, NACK/DTXnPUCCH,1(1)1, 0ACK, NACK/DTX, ACK, ACKnPUCCH,3(1)0, 1NACK/DTX, NACK/DTX, NACK/DTX, NACKnPUCCH,3(1)1, 1ACK, NACK/DTX, ACK, NACK/DTXnPUCCH,2(1)0, 1ACK, NACK/DTX, NACK/DTX, ACKnPUCCH,0(1)0, 1ACK, NACK/DTX, NACK/DTX, NACK/DTXnPUCCH,0(1)1, 1NACK/DTX, ACK, ACK, ACKnPUCCH,3(1)0, 1NACK/DTX, NACK, DTX, DTXnPUCCH,1(1)0, 0NACK/DTX, ACK, ACK, NACK/DTXnPUCCH,2(1)1, 0NACK/DTX, ACK, NACK/DTX, ACKnPUCCH,3(1)1, 0NACK/DTX, ACK, NACK/DTX, NACK/DTXnPUCCH,1(1)0, 1NACK/DTX, NACK/DTX, ACK, ACKnPUCCH,3(1)0, 1NACK/DTX, NACK/DTX, ACK, NACK/DTXnPUCCH,2(1)0, 0NACK/DTX, NACK/DTX, NACK/DTX, ACKnPUCCH,3(1)0, 0DTX, DTX, DTX, DTXN/AN/A
Currently, aggregation of up to 5 carriers is supported by an LTE-A (long term evolution advanced) system. An LTE-A UE needs to feed back ACK/NACK corresponding to multiple downlink carriers and downlink subframes in one uplink subframe, and a relatively larger amount of information needs to be fed back. Therefore, a new PUCCH format 3 is defined in LTE-A as a scheme for multi-bit ACK/NACK transmission. Up to 20 bits can be transmitted using PUCCH format 3. With A UE configured with PUCCH format 3 for ACK/NACK transmission, 4 PUCCH resources are semi-statically configured by a base station via higher layer signaling. The base station then dynamically informs the UE of which resource is used for PUCCH transmission via PDCCH during data scheduling.
An LTE-A system also supports PUCCH format 1b with channel selection for ACK/NACK multiplexing transmission of no more than 4 bits, and 3 new ACK/NACK mapping tables are defined as shown in Tables 5-7. Compared with previous mapping tables, the new mapping tables do not include overlapping states, thus providing better performances.
TABLE 5LTE-A ACK/NACK mapping table, A = 2HARQ-ACK(0)HARQ-ACK(1)nPUCCH(1)b(0), b(1)ACKACKnPUCCH,1(1)1, 0ACKNACK/DTXnPUCCH,0(1)1, 1NACK/DTXACKnPUCCH,1(1)0, 1NACKNACK/DTXnPUCCH,0(1)0, 0DTXNACK/DTXNo Transmission
TABLE 6LTE-A ACK/NACK mapping table, A = 3HARQ-b(0),ACK(0)HARQ-ACK(1)HARQ-ACK(2)nPUCCH(1)b(1)ACKACKACKnPUCCH,2(1)1, 1ACKACKNACK/DTXnPUCCH,1(1)1, 0ACKNACK/DTXACKnPUCCH,2(1)1, 0ACKNACK/DTXNACK/DTXnPUCCH,0(1)1, 1NACK/DTXACKACKnPUCCH,2(1)0, 1NACK/DTXACKNACK/DTXnPUCCH,1(1)0, 1NACK/DTXNACK/DTXACKnPUCCH,2(1)0, 0NACKNACK/DTXNACK/DTXnPUCCH,0(1)0, 0DTXNACK/DTXNACK/DTXNo Transmission
TABLE 7LTE-A ACK/NACK mapping table, A = 4HARQ-HARQ-HARQ-HARQ-b(0),ACK(0)ACK(1)ACK(2)ACK(3)nPUCCH(1)b(1)ACKACKACKACKnPUCCH,1(1)1, 1ACKACKACKNACK/DTXnPUCCH,2(1)1, 1ACKACKNACK/DTXACKnPUCCH,0(1)1, 0ACKACKNACK/DTXNACK/DTXnPUCCH,1(1)1, 0ACKNACK/DTXACKACKnPUCCH,3(1)1, 1ACKNACK/DTXACKNACK/DTXnPUCCH,2(1)1, 0ACKNACK/DTXNACK/DTXACKnPUCCH,0(1)0, 1ACKNACK/DTXNACK/DTXNACK/DTXnPUCCH,0(1)1, 1NACK/ACKACKACKnPUCCH,1(1)0, 0DTXNACK/ACKACKNACK/DTXnPUCCH,2(1)0, 1DTXNACK/ACKNACK/DTXACKnPUCCH,3(1)1, 0DTXNACK/ACKNACK/DTXNACK/DTXnPUCCH,1(1)0, 1DTXNACK/NACK/DTXACKACKnPUCCH,3(1)0, 1DTXNACK/NACK/DTXACKNACK/DTXnPUCCH,2(1)0, 0DTXNACK/NACK/DTXNACK/DTXACKnPUCCH,3(1)0, 0DTXNACKNACK/DTXNACK/DTXNACK/DTXnPUCCH,0(1)0, 0DTXNACK/DTXNACK/DTXNACK/DTXNo Transmission
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.